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Hepatitis A and E 

Hepatitis A and E
Chapter:
Hepatitis A and E
DOI:
10.1093/med/9780198729228.003.0073
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date: 26 June 2019

Hepatitis B virus (HBV) is a global health problem and can cause a wide spectrum of liver disorders, including acute hepatitis, fulminant hepatitis, chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. In areas of high prevalence, transmission is predominantly from mother to child. In low-endemicity countries, most infections are acquired in adulthood by sexual transmission or sharing of contaminated equipment by intravenous drug users. Most cases of acute hepatitis B infection are asymptomatic or subclinical, although rarely there is a fulminant presentation. In acute hepatitis B, hepatitis B surface antigen (HBsAg) clears within 6 months; chronic infection (defined as persistence of HBsAg in the serum for 6 months or longer) occurs in 90% of those infected at birth, in 20–50% of those infected between the ages of 1 and 5 years, and in less than 5% of adults. Chronic hepatitis B has three phases: (i) an immune-tolerant phase—with high viral replication, mainly seen in children infected at birth who are usually asymptomatic; (ii) an immune-active phase—with elevated aminotransferases and marked inflammation, which, if persistent, may lead to fibrosis; and (iii) an inactive carrier state—with normalization of aminotransferases, reduction in HBV DNA, and improvement in hepatic inflammation. Treatment with interferon or nucleos(t)ide analogues during the immune-tolerant phase is considered to be ineffective but may be effective in normalizing serum alanine aminotransferase levels in immune-active disease. Public health measures for reducing transmission of HBV include: immunization, screening of high-risk groups, and post-exposure prophylaxis for those at risk.

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